The present invention relates generally to rotational control apparatuses and particularly to coupling clutches and more specifically to clutches engageable in driving positions with which the input and output always come to the same degrees of registry for rotation of the output.
It is often desirable to couple first and second mutually rotating parts such as shafts and to controllably rotatably relate them together. Coupling clutches can be utilized in these situations. However, coupling clutches suffered from problems resulting from the horizontal and angular misalignment of the shafts. Furthermore, in the printing industry, for example, where sheet material must be put through a run a second time and register with a previous sheet position, it is desired to allow a declutched element to be clutched in to the same previous position relative to a member of the machine running the sheet material.
Prior clutches which accomplish this need generally include a ball carrier on the output side of the clutch, the balls of which keep the face of the input drive ring perpendicular to the sliding axis of the hub which provides lateral support between the drive ring and the ball carrier. The balls prevent a torque output during the seeking of registry of the balls of the ball carrier with the cavities of the drive ring. With registry, the teeth of the drive ring engage teeth of this ball carrier output member.
However, such prior clutches may be prone to unwarranted clutch engagement as the result of the balls dislodging from the ball carrier due to wear, clutch failure, and the like and jamming between the input and output interfaces. Such undesired engagement may cause damage to the machinery which the apparatus controls, the work piece which is being operated upon by such machinery, and/or the personnel operating or attempting to repair or maintain such machinery. Thus, a need has arisen for clutches preventing undesired and unwarranted clutch engagement as the result of dislodged balls jamming between the input and the output of the clutch.